Transport installations making use of passive vehicles hauled along a track by traction cables are well known in the art.
FR 2 658 772 discloses a funicular including two hauling cables independent of one another and driven by separate motors for moving two vehicles between two stations. The tracks a middle siding section where the two vehicle can circulate simultaneously in different section and two end sections where only one vehicle can be at any given time. One of the cables is coupled to one of the vehicles, and the other cable to the other vehicle. Each vehicle is independent of the other and can move or even stop independently of the other vehicle. However, it is not easy to efficiently operate the installation when the number of passengers heavily fluctuates. Moreover, the installation is not adapted to long distances, since one vehicle only can travel at any given time in one direction.
The U.S. Pat. No. 3,871,303 describes a transport installation comprising individual passive vehicles able to move along a track, each vehicle being equipped with a detachable grip for coupling on to a first haulage cable in continuous movement, corresponding to a cruising speed for the vehicles and stretching along the cruising sections of the said track so as to haul in synchronism the successive vehicles coupled on to the cable. A device operates the grip actuating the coupling and uncoupling respectively of the vehicle at the entrance to and at the exit from a cruising section by the attaching to and detaching from the said haulage cable of the grip. A second haulage cable stretches along auxiliary sections of track and in cable changeover zones parallel with the first cable, the said vehicle being capable of being coupled on to the said second cable. The transport vehicle is equipped with several independent coupling grips, each of these being able to work in conjunction with a predetermined cable, respectively for haulage on the line, for deceleration and for acceleration. However, the use of independent grips may be the origin of incidents and necessitates safety controls and interlocking systems, the compatibility of which with operating conditions presents difficulty.
U.S. Pat. No. 4,092,929 discloses a transport installation comprising individual passive vehicles each equipped with a triple grip for coupling the vehicle to a main haulage cable extending along the track or to auxiliary haulage cables for instance acceleration and deceleration cables at a station. One pair of jaws of the grip is open when the two other pairs of jaws are in the coupling position and conversely.
EP 1 193 153 discloses an installation for moving vehicles pulled by a cable, comprising two or more stations, the vehicles travelling on at least one track between the stations, each vehicle comprising at least one gripper, able to move between at least two positions and able to come into engagement with a tractor cable. The installation comprises several tractor cables each mounted in a loop, the said loops extending vertically parallel to the track, one after the other, the ends of two successive cable loops being sufficiently close to each other to enable the gripper to release the cable of the previous loop and to grip the cable of the following loop. More specifically, the installation comprises a first and second succession of cable loops for pulling the vehicle in respectively an outward and a return direction, the vehicles changing direction at the end of the line, and a single travel track, the two cable loops providing the traction in the outward and return directions respectively extending parallel to the single track, close to each other, so that the gripper can easily pass from one cable to another. The single track divides locally into two outward and return tracks, each associated with a respective outward and return tractor cable loop, so that two vehicles travelling in opposite directions can pass each other, the two outward and return tracks joining again in order to form a single track again. This installation is particularly flexible since, a vehicle, to decelerate, call at intermediate stations and accelerate again on the track independently from the other vehicles. A vehicle is even able to change direction of movement whilst travelling on the single track. However, this flexibility comes at a very high price in terms of complexity of the installation and of its operation.
In German patent DE 644,714, a transport installation for use in potash mines is described. The installation includes two independent rope loops driven in parallel in the same direction along an outbound and an inbound path. Mine cars travelling on the two paths are permanently secured to one or the other of the two ropes. Successive mine cars are alternatively secured to one or the other of the two ropes. Hence, the capacity of the installation is doubled. However, any incident on one of the ropes results in the whole installation being stopped. Moreover, the installation is not adapted to the transport of passengers since the mine cars are not supposed to stop at the end of the outbound or inbound paths.